David Burzillo, BHP Teacher
Massachusetts, USA

Kepler-186f was the first rocky planet to be found within the habitable zone. Credit: NASA Ames/SETI Institute/JPL-Caltech. Public Domain .

When I started teaching many years ago, the only known planets in the Universe were considered to be in our Solar System. In the last 20 years, more than 3,200 exoplanets have been confirmed, another 2,400 are being vetted, and over 2,400 solar systems have been discovered. Amazing! Even more fascinating than this proliferation of planets are the techniques that astronomers are using to detect exoplanets and determine their characteristics. Like so many of the great discoveries described in the Big History Project course, the ingenious methods astronomers are using to study exoplanets are a great testament to the creativity and ingenuity of humans in their quest to understand the world—and Universe—around them.

Light curve of a planet transiting its star. Credit: NASA Ames. Public Domain.

Interpreting planet transit data is one example of this ingenuity, and Interpreting Transit Graphs, an activity in Lesson 4.5, is a great way to take students’ understanding of transit from conceptual to concrete. By completing the activity worksheets on transiting exoplanets, students come to understand how astronomers “see” distant planets. A very distant star is incredibly small when observed by an Earth-based telescope, and, as you can imagine, any planet orbiting such a star would be miniscule in comparison. But astronomers have developed a method for noting the presence of these miniscule planets. By measuring the light reaching the Earth from a star and noting the periodic fluctuations in the amount of light, astronomers are able to “see” a planet passing in front of the star. By measuring these periodic fluctuations, astronomers can determine if, in fact, more than one planet is causing the changes. They can also determine the diameter of the planet and they can determine how far the planet is from the star. Knowing how big the planet is and how far it is from its star is critical for understanding if life on it is possible. With this knowledge, astronomers who are searching for evidence of life in other parts of the Universe are able to focus on those planets in a particular star’s “Goldilocks zone.”

Interpreting Transit Graphs is a number-heavy activity that will require the close attention of you and your students. But there’s a great payoff: a deeper understanding of the creativity of astronomers and the exciting work they are pursuing to discover the possibility of life in other worlds.

About the author: Dave has taught for over 30 years, more than 25 of them at his current school, a private high school in Weston, MA. For the last 7 years, he has taught BHP to ninth-, eleventh-, and twelfth-graders. His school runs on a trimester system, which gives him about 90 days to cover 13.8 billion years of history. Recently, Dave began offering an online Big History Project course in the summer.

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